1. Field of the Invention
The present invention relates to a donor film for a flat panel display and a method of fabricating an Organic Light Emitting Device (OLED) using the same and, more particularly, to a donor film for a flat panel display with improved adhesion with a transfer layer and a method of fabricating an OLED using the same.
2. Description of the Related Art
In general, an Organic Light Emitting Device (hereinafter referred to as “OLED”) as a flat panel display includes anodes, cathodes and organic layers interposed between the anodes and cathodes. The organic layers must include an emission layer and may further include a hole injecting layer, a hole transporting layer, an electron transporting layer and an electron injecting layer therewith. The OLED may be classified into a polymer OLED and a small molecular OLED based on a material composing the organic layer, more specifically the emission layer of the organic layer.
In implementing full color for the OLED, the emission layer must be patterned. There are methods for patterning the emission layer of the OLED. The small molecular OLED is patterned using a shadow mask and the polymer OLED is patterned by ink-jet printing or Laser Induced Thermal Imaging (hereinafter referred to as “LITI”). The LITI method has advantages of finely patterning the organic layer in a dry process. On the other hand, the ink-jet printing method patterns the organic layer in a wet process.
The method for patterning the polymer organic layer using the LITI needs at least a light source, an OLED substrate (i.e., an acceptor substrate) and a donor film. Here, the donor film includes a base film, a Light-To-Heat Conversion layer (hereinafter referred to as “LTHC”) and a transfer layer comprising an organic layer. The organic layer on the acceptor substrate is patterned as follows: when the light source irradiates light to the LTHC layer of the donor film, the LTHC layer absorbs the incident light and then converts the light into heat energy. Then the heat energy transfers the organic layer of the transfer layer onto the acceptor substrate. This process is disclosed in Korean Patent Application No. 10-1998-0051844, U.S. Pat. Nos. 5,998,085, 6,214,520 and 6,114,088, which are hereby incorporated by reference.
FIGS. 1A and 1B are cross-sectional views for explaining a transfer mechanism in a transfer process of a typical organic layer by the LITI method.
Referring to FIG. 1A, an organic layer S2 is attached to a donor substrate S1, which is composed of a base film S1a and an LTHC layer S1b, with first adhesion W12 between the donor substrate S1 and the organic layer S2. An acceptor substrate S3 is disposed under the donor substrate S1.
Referring to FIG. 1B, laser light is irradiated onto a first area R1 of the base film S1a except for a second area R2. The laser light passed through the base film S1a is converted into heat energy in the LTHC layer and then the heat induces a change in the first adhesion W12 of the first area R1 such that the organic layer S2 is transferred onto the acceptor substrate S3. In the transfer process, the transfer characteristic of the organic layer S2 depends on the first adhesion W12 between the donor substrate S1 of the second area R2 and the organic layer S2, cohesion W22 within the organic layer S2, and second adhesion W23 between the organic layer S2 and the acceptor substrate S3.
However, if the first adhesion W12 is relatively smaller, the organic layer S2 may be easily detached from the donor substrate S1. As a result, the organic layer S2 of the second region R2 without the laser irradiation is transferred even though it is not intended. This problem appears more seriously in the organic layer S2 including small molecular materials.